Preheat oven to 375°.
Mix the flour, baking powder, salt and baking soda, in a medium sized bowl until blended.
Mix the wet ingredients, including the butter, granulated sugar, light brown sugar, egg, egg yolk and vanilla in large bowl until combined well.
Stir in the flour mixture in thirds, mixing in between each add, until everything is well combined. The dough should be thick and not sticky, but should not be crumbly.
Mix in the graham cracker crumbs, marshmallows and chocolate chips until they are evenly distributed.
Drop dough by rounded tablespoonfuls on ungreased cookie sheets.
Bake 10 to 12 minutes until edges are lightly golden.
Enjoy a few warm, then cool the completely on a wire rack, then store in an airtight container.